Fix for a content view migration issue

Previously, a removal of a content view would not cascade properly across changesets
This caused dangling references in changesets. This commit fixes that issue
by removing all references in a changeset which has a content view that no longer exists.
(cherry picked from commit 8ced2f38368418e94bf9d7d0fc49b38ccebd27cb)
Automatic commit of package [katello] release [1.4.13-1].